Media exchange: This service includes RTP streams between endpoints that are located in different sites.

Other services: These services include instant messaging, presence, and IP phone XML services, and access to applications such as attendant console, Cisco Unified Communications Manager Assistant, and others.

If the IP WAN connection is broken, these services are not available. This unavailability might be acceptable for some services, but strategic applications such as telephone call services should be made available during WAN failure via backup methods.

Availability Issues Example: IP WAN Failure

The figure illustrates an example of lost services during WAN failure.

IP WAN failure impacts the connection to the remote cluster, phones at remote sites, and access to the ITSP or any destination on the Internet.

In the example, there is a main site with an intercluster trunk to a remote Cisco Unified Communications Manager cluster. There is also a remote site with IP phones that register at the Cisco Unified Communications Manager cluster that is located at the main site. A SIP trunk is used to connect to an ITSP.

If a WAN failure occurs, no calls to the other cluster or to the ITSP are possible. In addition, all phones that are located at the remote site lose registration with Cisco Unified Communications Manager, so they do not operate at all. They cannot even place calls within the remote site.

Note

A deployment as shown in the example is badly designed because of the lack of IP WAN backup.